Synthesis of aliphatic organic acids and esters



Patented Nov. 1,,193 8 P TENT OFFICE SYNTHESIS OF ALIPHATIC ORGANICACIDS AND ESTERS Donald J. Loder, Wilmington, Del., asoignor to E. L duPont de Nemours a Company, Wilmington, DeL, a corporation of Delaware NoDrawing. Application July 13, 1935,

Serial No. 31,208

16 Claims.

This invention relates to a process for thefor- 1 mation of organiccompounds and particularly to the preparation of monocarboxylic acids bythe interaction of aliphatic alcohols and carbon monoxide in thepresence of a catalyst.

It is known that organic acids and esters can .be prepared by theinteraction, in the vapor phase,of organic compounds with the oxides ofcarbon. For example, it has been shown that by the condensation ofmethyl alcohol with carbon monoxide in the presence of-a suitablecatalyst, acetic acid and methyl acetate, may be prepared in proportionswhich are governed .by the particular operating conditions.

An object of this invention is to provide improvements in processesforthe preparation of higher molecular weight organic compounds thru theintroduction of carbon monoxide into the lower molecular weight organiccompounds. A

further object of the invention is to provide a process for thepreparation of monocarboxylic acids by the condensation of an aliphaticalcohol with a carbon oxide 'in the presence of a catalyst. Anotherobject of the invention is to provide a process for the preparation ofacids having the chemical formula: CIHa +1COOH from alcohols having thechemical formula: CnHRn-i-IOH by subjecting the alcohols to the actionof the carbon monoxide in the presence of a compound containing boronand a halogen as the catalyst, with or without the presence of anabsorbent ma terial suchas pumice, silica gel, active carbon,

etc. Other objects will hereinafter appear.

The above objects can be realized by reacting a vaporized aliphaticmonohydroxyalcohol, carbon monoxide, and a volatile catalyst containingboron and ahalogen, under suitable pressure and temperature conditions,over, if desired, an absorbent material such as active carbon or moreparticularly over activated charcoal. The products resulting from such areaction will contain generally a mixture of, among other compounds,aliphatic carboxylic acids some of which have a greater, some a lesser,number of carbon atoms than are present in the alcohol treated, analiphatic acid containing one morecarbon atom than the alcohol, usually,predominating. The volatile catalyst containing boron and fluorine whichare suitable for activating the reaction include the halides of boron,including boron chloride, boron fluoride, boron iodide, boron bromide,as well as the acids of these halides, such for example, as,dihydroxyiluoboric acid, boroiiuorohydric acid (mm), mixtures of Hi?and (c1. zoo-532) boric acid in any degree of dehydration up to BF: withor without BFa.

Boron fluoride, as well asthe other catalysts, may be used alone andbecause of their excellent activity do not generally require additionagents or promoters to extend their activity. In some instances it maybe desirable, as has been indicated, to pass the vapors over anabsorbent material such as activated carbon. Other so called supportsmay be used such as alumina, activated silica, etc., with or withoutpromoters such as powdered nickel, nickel oxide and the like.

The alcohol-carbon monoxide reaction which can be accelerated by theabove described catalysts may be expressed as follows: CnH2n+loH+ COC,.Hzn+1COOH. In accordance with the particular operating conditions, itwill be found that, in some instances, the acid may not be formeddirectly in the free state, but may be produced as the ester of thealcohol. The alcohols used may be replaced, if desired, wholly or partlyby the corresponding alkyl ethers of the alcohols, such as dimethylether, diethyl ether, or the mixed alkyl ethers, the alkyl esters, alkylamines or the alkyl halides. It is generally advantageous, although notessential, to have water vapor present during the alcohol-carbonmonoxide to acids reaction.

The synthesis can generally be efliciently carried out under thefollowing operating conditions. The pressure may vary from approximately atmospheres to 900 atmospheres or higher with the preferablyoperating range in the neighborhood of 350-700 atmospheres. For example,the process can be suitably carried out, with the catalysts of thisinvention, at temperatures of between 200-400 C., but still higher orlower temperatures may also be used in some cases, the speed of thereaction being increased, as would be expected, by the use of highertemperatures. In any event the temperature and Pressure conditions usedare-such as will assure the reaction being eifected'inthe vapor phase.

The carbon monoxide used may be obtained from variouscommercial sources,such, for example, as water gas, producer gas, coke oven gas, etc., butto obtain products of the highest degree of purity it is preferable toremove from such.

commercial gases the objectionable constitutents such as sulfurcompounds, metal carbonyls, etc.

The presence of inert gases in the alcohol-carbon monoxide mixture issometimes desirable. Nitrogen, for instance, has little deleteriouseifect on the reaction or yield and, in fact, may be advantsgeou'slyused in order to aid in the temperature control and to prevent too greata conversion of the alcohols and carbon monoxide on one pass through theconversion apparatus. Other strictly inert gases usually act similarly.It is, of course, understood that instead of introducing methanol itselfinto the reaction chamber substances or mixtures of substances whichdecompose or react to form alcohols or which decompose to form esters orethers may be employed, but generally I prefer to introduce methanoldirectly into the gas stream.

Not only can methanol be catalyzed in the presence of carbon monoxideand my catalyst to acetic acid, or methyl acetate, but one or more ofthe higher alcohols, such as ethyl alcohol, propyl alcohol, butylalcohol, and even the higher molecular weight straight and branchedchain alcohols, such, for example, as 2,4 dimethyl pentanol-l, hexylalcohol or octyl alcohol, may

be similarly converted into acids having correspond-ingly one morecarbon atom than the alcohol treated. In'fact, my. process and catalystmay be employed with any of the monohydric alcohols, providing thesealcohols volatilize without decomposition under the conditions existingduring the reaction. When converting the higher aliphatic alcohols, someof which are not water soluble, and particularly if water is desired inthe reaction, it is preferable, generally, to introduce the alcohol andwater into the carbon monoxide as a vapor or spray.. Any other suitableprocedure may be employed, however, for intimately commingling thevapors of the alcohols and water with. the oxide of carbon. Whenpreparing products from the higher molecular weight compounds I mayutilize in lieu of the alcohols, the ethers, halides, or esters,thereof,

the use of which will result in a good conversionwith generally someslight modification in the ratio of acid to other products obtained.

I shall now describe a specific embodiment v of my process but it willbe understood that the details therein given and. the compoundsemployed, either as reactants or catalysts, in no way restrict the scopeof this invention, but merely illustrate a method by which my processmay be carried out.

A gaseous mixture, containing %carbon monoxide, and 5% each of methanol,water vapor, and ydrogen, is passed together with approximately of boronfluoride into a conversion chamber containing activated charcoal andsuitable for the carrying out of gaseous exothermic reactions .underelevated pressures. The reaction is conducted at a temperature ofapproximately 325 0., and a. pressure of approximately 700 atmospheres.Upon condensation of the products of the reaction a good yield of aceticacid is obtained together with a small amount of other aliphatic acids.

The apparatus, which may be employed for it will be realized that manychanges may be made in my process without departing from the inventionor sacrificing any of its advantages.

. I claim:

1. In a process for the preparation of aliphatic organic acids the stepwhich comprises reacting carbon monoxide, in the vapor phase and in thepresence of boron fluoride, with a compound selected from the groupconsisting of a saturated, aliphatic alcohol and a compound which givesa saturated, aliphatic monohydric alcohol, upon decomposition, under theconditions of the reaction.

2. In a process for the preparation of aliphatic organic acids the stepwhich comprises reacting carbon monoxide, in the vapor phase and in thepresence of borofiuohydric acid, with a compound selected from the groupconsisting of a saturated, aliphatic monohydric alcohol and a compoundwhich gives a saturated, aliphatic monohydric alcohol, upondecomposition, under the conditions of the reaction.

3. In a process for the preparation of aliphatic organic acids the stepwhich comprises reacting carbon monoxide, in the vapor phase and in thepresence of-dihydroxyfiuoboric acid, with a compound selected from thegroup' consisting of a saturated, aliphatic monohydric alcohol and acompound which gives a saturated, aliphatic monohydric alcohol, upondecomposition, under the conditions of the reaction.

4. In a vapor phase process for the preparation of acetic acid the stepwhich comprises contacting methanol and carbon monoxide, with boronfluoride at a temperature between 200 and 400 C..

5. In a vapor phase process for the preparation of acetic acid the stepwhich comprises contacting methanol and carbon monoxide withborofluohydric acid at a temperature between 200 and 400 C.

6. In a vapor phase process for the preparation of acetic acid the stepwhich comprises contacting methanol and carbon monoxide withdihydroxyfiuoboric acid at a temperature between 200 and 400 C. v

7. A process for the preparation of acetic acid which comprises passinginto a reaction zone a gaseous mixture containing approximately 85 partsof carbon monoxide, 5 parts of methanol and 2 parts of boron fluoride,maintaining the gaseous mixture at a pressure of from 350 to 700atmospheres and at a temperature of from 200- 400 C., and finallyrecovering the acetic acid from the reaction product. v

8. A process of reacting in the vapor phase an aliphatic monohydricalcohol and carbon monoxide in the presence of boron fluoride andthereby producing a compound of the-group consisting of aliphaticorganic acids and their esters.

9. A process of reacting in the vapor phase methanol and carbon monoxidein the presence of boron fluoride and thereby producing a compound ofthe group consisting of acetic acid and methyl acetate.

10. A process of reacting in the vapor phase methanol and carbonmonoxide in the presence of boron fluoride and thereby producing aceticacid.

11. In a process for the preparation of oxygenated aliphatic organiccompounds the step which comprises passing in the vapor phase boronfluoride, carbon monoxide, and a compound selected from the groupconsisting of a saturated, allphatic monohydric alcohol and a compomuiI! which gives a saturated. aliphatic monohydr c alcohol, uponhydrolysis. into a reaction none and therein eiiecting the reaction.

12. Aprocessoi'reactlnginthevaporphasea compound selected from the groupconsisting of an aliphatic monohydric alcohol and a compound which, uponhydrolysis. gives an aliphatic monohydric alcohol with carbon monoxidein the presence of boron fluoride and thereby producing a compound 01'the group consisting of aliphatic organic acids and their esters.

i3. A process for the preparation of acetic acid which comprisesreacting in the vapor phase methanol and carbon monoxide at atemperature between 200 and 400 C. and a pressure 01' 350. to 700atmospheres while in the presence of boron fluoride.

14. In a process for the preparation of anorganic compound selectediroiriv the group consisting of aliphatic organic acids and theiresters. the step which comprises reacting carbon-monoxide in the vaporphase with a compound selected from the group consisting of a saturated.aliphatic monohydric alcohol and a compound which gives a saturated.aliphatic monohydric alcohol. upon decomposition. under the condiamount0; chemically combined boron and fluorine atoms. which catalyst is inthe vapor 16. In a process tor the preparation of acetic acid the stepwhich comprises reacting in the vapor phase methanol and carbon monoxidewith a catalyst containing a catalytically eflective amount ofchemically combined boron and which catalyst'is in the vapor fluorineato' phase.

DONALD J. LODER.

process for the,preparation oi a li- I

